The lower substrate 100 may include a suitable material such as a glass material, a metal material, or a plastic material (e.g., polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or polyimide). The upper substrate 300 may include a transparent material. For example, the upper substrate 300 may include a suitable material such as a glass material or a plastic material (e.g., PET, PEN, or polyimide). The lower substrate 100 and the upper substrate 300 may include the same material or different materials.

Referring to the display area DA of FIG. 3, a buffer layer 101 may be formed on the lower substrate 100. The buffer layer 101 may prevent moisture or a foreign material from penetrating through the lower substrate 100. For example, the buffer layer 101 may include an inorganic material such as silicon oxide (SiOx), silicon nitride (SiNx), or/and silicon oxynitride (SiON), and may have a single layer structure or a multi-layer structure.

A TFT 130 and a storage capacitor 140 may be provided to correspond to the display area DA. A display device 200 may be electrically connected to the TFT 130. The display device may be an OLED. The storage capacitor 140 may be located on the lower substrate 100. The TFT 130 of FIG. 3 may correspond to one of TFTs, e.g., the driving TFT Td, provided in the pixel circuit PC of FIG. 2. The storage capacitor 140 of FIG. 3 may correspond to the storage capacitor Cst of FIG. 2.